1. Technical Field
The present invention relates to a pattern formation method, a liquid droplet ejection apparatus and an electro-optical device.
2. Related Art
A process for manufacturing a display device or a semiconductor device includes many pattern formation processes in which a film pattern is formed by depositing a film on a substrate and then patterning it into a desired shape.
Recently, due to productivity improvement, that kind of pattern formation process has been using an inkjet method in which a film pattern is formed self-aligningly by ejecting and solidifying liquid droplets on a substrate. The inkjet method enables formation of a film pattern corresponding to a liquid droplet shape. Thus, the method does not require the formation of a mask for patterning, thereby reducing the number of pattern formation processes.
However, when a film pattern is formed by the inkjet method, without wet-extension of a liquid droplet landed on a substrate surface, an uneven shape of the liquid droplet reflects in a shape of the pattern. Consequently, the formed film pattern is likely to have degraded flatness and film thickness uniformity.
Thus, regarding such an inkjet method, there is provided a conventional method by spreading the wet-extension of a landed droplet (e.g. a patent document as below). In the patent document, the direction of liquid droplet ejection is tilted with respect to a normal line of a substrate, whereby a component along a counter-scanning direction on the substrate is provided to the ejected liquid droplet. In this manner, the landed liquid droplet can wet-extend along a tangential direction of the substrate by as much as an angle (tilt angle) defined by the normal line direction of the substrate and the ejection direction.
JP-A-2005-131498 is an example of related art.
Meanwhile, in the above inkjet method, typically, a liquid droplet ejection head for ejecting liquid droplets moves (for scanning) relatively with respect to the substrate to form a desired pattern. Thus, in the formation of a large film pattern, a single liquid-droplet ejection head performs line-feeding for scanning multiple times. Alternatively, a plurality of liquid-droplet ejection heads sequentially performs scanning. In other words, a pattern (individual pattern) formed by every scanning by each liquid-droplet ejection head is sequentially connected to the next to form a large film pattern.
However, liquid droplets positioned at an outer periphery (interface) of each individual pattern are evenly pulled (flown) inwardly on a corresponding pattern due to a surface tension or the like. Accordingly, the film pattern formed by sequentially connecting a plurality of individual patterns has a variation in its film thickness (line-feed streak) by as much as the outer periphery (interface) between the connected individual patterns. As a result, there arises a problem that the film pattern will have a degraded uniformity in its film thickness.